An example of a method for reversible fluidization/non-fluidization via irradiation of a material with light is a method in which ultraviolet light and visible light are applied to a liquid crystalline azobenzene compound (see Patent Document 1) having a sugar alcohol skeleton (Patent Document 2 and Non-Patent Document 1). FIG. 1 schematically shows such method; wherein, from the left to the right, (a) shows a powdered solid, (b) shows a liquid, and (c) shows a solid. In the figure, “A” represents irradiation of ultraviolet light and “B” represents irradiation of visible light.
This material is a single molecule with a molecular weight of several thousands. A possible application thereof is an adhesive agent that can adhere and be peeled reversibly with the application of light. It has been difficult to peel a conventional adhesive agent without a thermal or mechanical impact, and it also has been difficult to re-adhere or recycle such conventional adhesive agents. Such problems can be overcome with the use of a material that can repeatedly adhere and peeled reversibly with the application of light; however, the liquid crystalline azobenzene compound having a sugar alcohol skeleton described above is problematic in terms of its low adhesive force at the time of adhesion (50 N/cm2 in case of glass adhesion). FIG. 2 shows the adhesion strength test with the use of a material that is induced to liquefy or solidify with the application of light.
Patent Document 1: JP 2008-303209 A
Patent Document 2: JP 2011-256291 A
Patent Document 3: JP 2005-82604 A